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J F ,•1. 1 1 0 PR_O_POSED MONITORING__ FLAN To determine if ground water contamination has occurred as a akage of gasoline at the Rainbo result of past underground le Baking Company plant , three ground water monitor wells will be I constructed after obtaining well permits from the San Joaquin i.,ocal Health District ( See Figure 5- 1 for well construction cletails ) . The monitor wells will also be used to determine the ground water gradient at the site , and Figure 5- 2 shows the proposed locations of the monitor wells . Assuming the �. regional ground water flow direction ( northeasterly ) exists at the site , the well to the southwest of the former tank Ilocations is considered an upgradient well , and the wells jlocated north and east of the former tank locations are considered downgradient wells . However , if after installation J of the three wells , the ground water gradient is not to the 11 northeast , southwest , or east ( the direction in which the wells are to be located ) , a fourth well will be installed in Ithe downgradient direction . I+ The borings for well construction will be accomplished by using a hollow stem auger and mud rotary drilling . Split spoon soil sampling will be performed at 5 ft intervals from the ground surface to the depth of ground water , and at selected locations to further characterize significant changes Iin lithology . Samples will also be taken just above and below the water table . If the soil samples at the ground water table indicate possible ground water contamination las detected by visual observation and/or p1D readings ) , the t boring will not be converted into a well , but filled to the. J ground surface with grout . Another boring will be drilled in the same direction but further away from the excavation - if 1 no contamination is detected in the soil ample ; at the grnun" water table in this boring , the boring will be converted iTit < to well . l� 5 - 1